1 Field of the Invention
The present invention relates generally to devices for sealing a branch pipe retrofitted to an existing pipeline. More particularly, the invention relates to a branch pipe seal which is self-adjusting for use on existing pipelines of various diameters and materials.
2. Prior Art
In original construction of piping systems, a branch pipe connection is accomplished using a Tee. When a branch pipe is added to an existing pipeline, a portion has to be completely disassembled to install a new tee or a "saddle clamp" device is typically used to complete the connection. To install the saddle clamp device, a hole is drilled in the existing pipeline and the saddle clamp, with an adapter for attaching to the branch pipe, is installed over the hole. Appropriate gasketing or other sealing material is used to provide a leak-tight seal around the hole. Typically, the saddle clamp exerts pressure on the gasket material to effectuate the seal.
Due to the configuration of the existing pipe, the tangent to sealing surface has a constantly changing angle with respect to the axis of the hole. This angle is dependent upon the diameter of the hole and the diameter of the pipeline. To accommodate the varying diameters of pipe and holes for branch pipes, numerous sizes of "saddles" were required. In addition, the diameter of the hole relative to the diameter of the pipeline often required specially designed gaskets or other sealing means to accomplish a leak-tight seal.
One prior-art approach involves sizing of the saddle and seals to accommodate specific pipe diameters. U.S. Pat. No. 4,613,171 to Corcoran provides a recent example of this type of device. The Corcoran invention requires a special gasket adapted for each hole diameter and a saddle and clamping device limited to a small range of pipe diameters.
A second example of the prior art is provided in U.S. Pat. No. 4,627,648 to Montpetit. The Montpetit device is usable on a small range of diameters of pipe. However, each individual device is limited to a single hole size.
A final example demonstrates a device constrained both by hole size and pipeline diameter. U.S. Pat. No. 4,103,940 to Bills provides a branch fitting having an underface generally conforming to the outer surface of the pipe and a tubular portion extending into the hole to provide self-alignment and self-jigging for brazing or soldering the device to the pipe.